ADU rules in Milford

Detached accessory apartments were flatly banned in Milford until an amendment that takes effect August 14, 2026. Section 3.1.1.7, adopted 2-10-2023, requires that 'Both the principal and accessory dwellings must be contained in one building.' On July 7, 2026 the Planning and Zoning Board voted 8 to 1 to amend 3.1.1.7 so that an accessory dwelling unit 'may be allowed in a detached structure, in accessory to a single-family principal dwelling located in Zones R-18, R-30 and RA where property/zone classification is minimum 18,000 square feet or greater', with only one accessory dwelling unit per property; on July 21, 2026 the Board set the effective date at August 14, 2026 by a 6 to 1 vote. That confines detached units to Milford's three largest-lot single-family districts (R-18 requires 18,000 sq ft, R-30 requires 30,000, R-A requires 43,560), so R-12.5, R-10, R-7.5 and R-5 lots, which cover much of the city, still cannot have one. A detached unit must also satisfy the ordinary accessory-structure limits: 15 ft maximum height, 10 ft rear and 10 to 15 ft side setbacks, and a footprint no greater than 50 percent of the principal building's footprint unless it is 600 sq ft or smaller.

An attached or internal accessory apartment is a permitted use, not a special permit use. Section 3.1.1 states that the Board 'shall permit' the listed uses in the One Family Residential Districts (R-A, R-30, R-18, R-12.5, R-10, R-7.5 and R-5), and 3.1.1.7 is on that list. The unit must be a conversion 'either completely within an existing principal building or added to the already existing principal building', the two units must share 'a common interior wall, or floor, or ceiling with habitable space on each side' with internal access 'through a common living space', and the accessory apartment may not have an exterior door on the street-facing front of the building. Only one accessory apartment is allowed per single-family dwelling, it must use the existing dwelling's driveway and utilities, and it may not have its own street number. The SFA-10, RMF-9, RMF-16 and RO districts incorporate the Section 3.1 use list by reference, so an accessory apartment is allowed there too, but subject to Site Plan review by the Board.

Section 3.1.1.7(4) sets a hard 800 sq ft cap: 'The maximum size of an accessory apartment is 800 square feet as measured from the exterior walls', and stairs and corridors providing exclusive access plus all habitable space count toward that limit. There is no percentage-of-principal-dwelling alternative and no minimum unit size (Milford removed its minimum habitable-area rules, its 2023 Plan of Conservation and Development having flagged them as prohibited by P.A. 21-29). Detached units allowed from August 14, 2026 face two further caps that will usually bind before 800 sq ft does: no accessory building may exceed 15 feet in height (Sec. 4.1.1.3), and no accessory building may have a footprint exceeding 50 percent of the principal building's footprint, except that an accessory building of 600 sq ft or less is exempt from that ratio (Sec. 4.1.1.4). Because 3.1.1.7(9) bars any application to the Zoning Board of Appeals to vary the section, there is no relief route from the 800 sq ft cap.

Section 3.1.1.7(3) requires that 'One of the dwelling units shall be owner-occupied.' The obligation is continuing, not merely a condition at application: if either unit stops being owner-occupied the owner must notify the Planning and Zoning Office, the accessory apartment use must be discontinued and the permit is revoked, after which the owner must strip out all cooking appliances and related electrical or gas services and have the Building Official certify the removal. Owner occupancy survives Connecticut's statewide accessory apartment law by design: CGS 8-2o(a)(6) lists the conditions a town may not impose and owner occupancy is deliberately absent from it, and Milford opted out of 8-2o entirely in the autumn of 2022. Unlike the pre-2023 rule, the current section no longer requires the second unit's occupant to be a relative and no longer expires after three years.

Milford's off-street parking table (Figure 4, Sec. 5.1.4) has no line for an accessory apartment, and no provision adds a space for one; the single-family requirement stays at 2 spaces. Section 3.1.1.7(6) instead requires that 'The accessory apartment shall utilize the existing dwelling's driveway and utilities, i.e., electric, gas, and water', so an ADU cannot be given its own curb cut or its own utility hookups. Because Milford opted out of CGS 8-2o, the statute's one-space ADU cap does not apply here, but Milford imposes nothing anyway. Parking was the main objection raised when the Board approved detached units on July 7, 2026, and the final motion answered it by limiting detached ADUs to the three largest-lot zones rather than by adding a parking standard.

An accessory apartment is listed under 3.1.1 Permitted Uses, not under 3.1.2 Special Uses, so no public hearing and no special permit are involved in the One Family Residential Districts. It is processed as a zoning permit: the city's zoning fee schedule lists 'Accessory Apartment $100.00' under the Zoning Permit heading, alongside accessory structures and additions, and well apart from the Site Plan Review, Special Permit and Special Exception fees. The application package is an A-2 survey plus full floor plans and full elevation views of the entire structure. Two caveats: in the SFA-10, RMF-9, RMF-16 and RO districts the Section 3.1 uses are incorporated 'subject to Site Plan review', which puts the application in front of the Board (a 65-day decision on objective standards rather than a discretionary hearing); and 3.1.1.7(9) prohibits any application to the Zoning Board of Appeals to vary any part of the section, so a proposal that misses a standard has no variance path.

Nothing in the current Section 3.1.1.7 restricts renting an accessory apartment. The pre-2023 version did: it required the second unit to be occupied by a relative by blood, marriage or legal adoption, said flatly that 'No accessory apartment shall be utilized for income purposes', and expired every three years. All of that was repealed by the amendment effective 2-10-2023. What remains is the owner-occupancy rule at 3.1.1.7(3), so the owner may rent out one unit but must live in the other. On short-term rentals, the Board of Aldermen adopted Code of Ordinances Chapter 11, Article V (Sections 11-160 to 11-172) on May 4, 2026 by a 9 to 6 vote, creating a $50 annual short-term rental permit for stays of 1 to 30 days. During that meeting the Board voted unanimously to exempt ADUs by adding to the definition of Dwelling Unit the words 'but shall not include ADU's' and deleting the draft subsection that would have prohibited short-term rental of ADUs. Because a Short-Term Residential Rental is defined as furnished living space 'in a Dwelling Unit', accessory apartments fall outside the ordinance and outside its permit requirement. When a Board member asked at the July 7, 2026 Planning and Zoning meeting whether ADUs can be used as Airbnbs, the answer given was yes.